<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <h2>词法作用域</h2>
</body>
<script>
    let username = 'jack'

    function fn() {
        console.log('我的值是多少：', username) //???
    }



    function getValue() {

        let username = 'alice'


        fn()
    }

    getValue()
</script>

</html>